The present invention relates generally to sets of at least 6 recombinant and/or synthetic peptides derived from Trypanosoma cruzi proteins which are used for diagnosing Chagas"" disease in a highly sensitive and specific manner. More specifically, the present invention relates to peptides derived from the T. cruzi antigens SAPA, CRA, FRA, TcD, Tc24, Ag39 and MAP which are used in a confirmatory immunoassay and concerns kits comprising the latter peptides.
Chagas"" disease is endemic throughout Latin America and a major cause of morbidity and mortality in those countries affected. Approximately 16-18 million people are infected, and about 50,000 patients die each year from the condition (Carvalho et al., 1993). Its etiologic agent, the protozoan parasite Trypanosoma cruzi, is naturally transmitted by various species of triatomine bugs. Disease transmission occurs when infectious forms of the parasite are deposited during the blood meal along with the insect""s feces. In Brazil, successful vector control programs have almost completely abolished naturally occurring transmission, with the exception of the hinterland. As a result, transfusion of blood from infected donorsxe2x80x94often migrants to larger citiesxe2x80x94has become the major route for contracting the parasite (Almeida et al., 1990). Recent surveys estimate the annual number of transfusion-acquired Chagas"" disease cases in Brazil at 20,000 out of a total of 5 to 6 million blood transfusions (Zingales et al., 1990). Consequently, an efficient donor screening program is crucial in eliminating contaminated blood while not negatively affecting the country""s blood supply.
In Brazilian blood banks, the screening for antibodies directed against T. cruzi is mandatory. Screening assays include indirect immunofluorescence (IFA), indirect hemagglutination (IHA), and enzyme-linked immunosorbent assays (ELISA). The utilization of at least two assays based on either different methodologies or different antigen preparations is currently recommended, but conflicting results are often observed. A few specialized laboratories have developed Western blot techniques (Peralta et al., 1994) in an attempt to resolve discrepant results, but no single test is sufficiently sensitive to prevent transfusion transmission of Chagas"" disease.
Most of the tests that are commercially available today employ crude parasite extracts or subcellular fractions as antigen preparations. However, it has been shown that parasite extracts cross-react with sera from patients harboring other diseases such as leishmaniasis, Trypanosoma rangeli infection, syphilis, or rheumatic fever. In recent years, various investigators have reported the cloning and characterization of T. cruzi-specific immunoreactive antigens (Borges-Pereira, 1997). Several studies have evaluated the diagnostic potential of these recombinant antigens either in the form of fusion proteins or as synthetic peptides (Almeida et al., 1990; Peralta et al., 1994). Although an increase in sensitivity and specificity of these assays was observed, cross-reactivity with Leishmania-specific antibodies still occurred. The present invention relates to sets of at least 6 recombinant and/or synthetic peptides derived from Trypanosoma cruzi antigens which are used for diagnosing Chagas""s disease in a highly sensitive and specific manner and which do not cross react with Leishmania-specific antibodies. The use of a new multiparameter assay combining relevant and immunodominant antigens derived from T. cruzi proteins as a diagnostic test for Chagas"" disease is herein described.
It is clear from the above that no single test is sufficiently sensitive to prevent transfusion transmission of Chagas"" disease which has become the major route of transmission for this infection. Current screening tests are insensitive, non-specific and yield conflicting results, while convenient confirmatory assays do not exist. The present invention therefore aims at providing sets of recombinant and/or synthetic antigens and their use for serological diagnosis of Chagas"" disease. More specifically, the present invention aims at providing assays which are able to reliably and accurately detect the presence of antibodies to various specific antigens of Trypanosoma cruzi in a highly sensitive and specific manner. In this regard, the present invention aims at providing sets of at least 6 recombinant and/or synthetic peptides derived from the T. cruzi antigens SAPA, CRA, FRA, TcD, Tc24, Ag39 and MAP for usage in a confirmatory immunoassay and aims at providing kits comprising the latter peptides. Moreover, it is also an aim of the present invention to provide sets of T. cruzi antigens which can be used in a vaccine composition for immunizing an individual to prevent Chagas"" disease upon exposure to T. cruzi. 